Generally speaking, would you say most people can be trusted? Or would you say you can't be too careful when dealing with other people? Those are questions the Pew Research Center has been asking for years to try to measure social trust. And a new study shows that the millennial generation, ages 18 to 33, has the lowest levels of social trust ever. NPR's Sami Yenigun filed this report.

SAMI YENIGUN, BYLINE: It's cold in Washington, D.C. The sun has set and people are rushing to the metro after a long day's work. 23-year-old Ari Scott and 25-year-old Natasha Sebastiani are stopping people on the street and asking for their credit card info.

SCOTT: We try not to just walk up people. We try to give them a very obvious notice that they will be getting talked to, and also that we're people that they can trust, that we're like not shifters or anything like that.

YENIGUN: Both Scott and Sebastiani are working for Children International, an organization that donates money to children living in poverty. Forging trust is central to their work. But when it comes to their personal lives...

NATASHA SEBASTIANI: It is very difficult for me to trust people. Every time that I run into people selling something on the street, which is what they think that we do, I run away and I stay away.

YENIGUN: And according to the Pew Research Center, that line of thinking is pretty common. In a study published late last week, only 19% of millennial adults say that, generally speaking, most people can be trusted. Every other generation tops 30%. Paul Taylor is executive vice president at the Pew Research Center. He says that for decades, young people have had lower levels of social trust but never this low.

PAUL TAYLOR: There is something about the way today's young adults are growing up that leaves them feeling less trustful of their fellow human beings.

YENIGUN: One explanation for this, the study suggests, is growing racial diversity - 43 percent of millennial adults are non-white, making this the most diverse generation in America. Camille Leak is 28 years old and studies millennials for the Futures Company. She says, minority groups have long had low levels of social trust.

CAMILLE LEAK: I think that, ultimately, it stems from their history of having to deal with persecution and discrimination, whether in their personal lives or within the business setting.

YENIGUN: Not only are non-white populations a bigger share of the whole, Leak says, they're also more influential.

LEAK: Within the millennial generation in particular, multicultural consumers have a much higher level of influence on their non-Hispanic white counterparts. So we're seeing that even outside of areas like trust, non-Hispanic white millennials have begun to adopt certain multicultural either behaviors or characteristics.

YENIGUN: You can see it on Facebook, in the slang and music that young white men and women post to their walls. And Pew reports that a staggering 81 percent of millennials are on Facebook. Leak suggests that the Internet itself is another reason millennials are so distrustful.

LEAK: I mean, there's a reason why catfish is now a verb.

YENIGUN: Catfish?

UNIDENTIFIED WOMAN #2: Catfish, to pretend to be someone you're not online, by posting false information, often to seduce someone into falling in love.

YENIGUN: The thinking goes that the first generation to grow up with the Internet is hip to the sometimes dishonest nature of the Web. Young people know not to trust everything or everyone that they see. So who's the one in five that says, yeah, people can be trusted? Sara Bakken's one of them. She lives in South Dakota. She says, if she were to meet someone on the street, chances are, she could trust them.

SARA BAKKEN: I might be a more trusting person but I do feel like South Dakota is kind of unique in that way, too. There aren't very many of us here.

YENIGUN: But Bakken says she's not sure that she'd lend anyone any money. Like many of her peers, she's drowning under college debt and guesses that a weak economy could be another reason so many young people have so little trust for their fellow man. Camille Leak says, low levels of social trust shouldn't be mistaken for a pessimistic world view.

LEAK: It's just being savvy and being realistic, and I think that's what it is for a lot of millennials. It's not about being optimistic or pessimistic. It's about being realistic.

YENIGUN: Despite this lack of trust, the study says, the millennial generation is the most upbeat about the future of the country. Sami Yenigun, NPR News.

(SOUNDBITE OF MUSIC)

ROBERT SIEGEL, HOST:

You're listening to ALL THINGS CONSIDERED from NPR News. Transcript provided by NPR, Copyright NPR.